Laminated magnet core

ABSTRACT

A laminated magnet core for contactors or the like has a working airgap. The magnet core is made up of stacked metal sheets having respective slitlike openings extending across a portion of the width of the sheets, the openings being at least partly overlapping and jointly defining a gap for reducing the core remanence.

United States Patent Otto Muller; Gunter Rauter, both of Amberg, Germany [21] Appl. No. 69,003

[72] Inventors [22] Filed Sept. 2,1970

[45] Patented Nov. 30, 1971 [73] Assignee Siemens Aktiengesellschaft Berlin, Germany [3 2] Priority Sept. 4, 1969 [3 3 Germany [54] LAMINATED MAGNET CORE 7 Claims, 4 Drawing Figs.

[52] [1.8. CI 335/281, 335/297, 336/234 [51] lnt.Cl H01i3/00 [50] Field of Search 335/227,

[56] References Cited UNlTED STATES PATENTS 2,313,527 3/1943 Edwards 335/227 X 2,952,801 9/1960 Hyink 335/281 X 3,188,427 6/1965 Cooper et al. 335/281 X FOREIGN PATENTS 241,584 12/1964 Austria 335/281 Primary ExaminerG. Harris Attorneys-Curt M. Avery, Arthur E. Wilfond, Herbert L.

Lerner and Daniel J. Tick ABSTRACT: A laminated magnet core for contactors or the like has a working airgap. The magnet core is made up of stacked metal sheets having respective slitlike openings extending across a portion of the width of the sheets. the openings being at least partly overlapping and jointly defining a gap for reducing the core remanence.

LAMINATED MAGNET CORE Our invention relates to laminated magnet cores made up of stacked metal sheets, especially U-shaped magnet cores for contactors and the like.

The invention is related to those disclosed and claimed in the copending applications of G. Bohlke, Ser. No. 6900 l filed Sept. 2, I970, claiming a German priority of Jan. 28, l970; and G. Rauter, Ser. No. 69002, filed Sept. 2, i970, claiming a German priority of May 2, 1970, these applications being assigned to the assignee of the present invention.

In the known arrangements of such magnet cores, for example as described in German Printed Pat. application No. 1,250,552, the airgap for reducing remanence forces is provided over the full cross section of the magnet core; this construction makes it necessary to hold the resulting core parts together by means of cover plates that have large openings at the location where the airgap is covered. This configuration causes the remaining bridging cross section to become highly saturated during the operation of the magnet.

This kndwn construction requires that relatively thick cover plates be provided to withstand the blows of the contacting magnet cores. In addition, attention must be given to achieving a good joining of the cover plates and the core parts.

It is an object of our invention to provide a magnet core for contactors or the like having an airgap for reducing remanence forces.

It is another object of our invention to provide a magnet core wherein the air gap for reducing remanence forces is easily producible. Subsidiary to this object, it is an object of our invention to provide such a magnet core wherein the aforementioned airgap does not change during operation of the magnet core.

According to a feature of our invention, a laminated magnet core is made up of stacked metal sheets having respective slitlike openings extending across a portion of the width of the sheets, these openings being at least partly overlapping and jointly defining a gap for reducing the core remanence. According to a further feature of our invention, the aforementioned openings are positioned in mutual alignment and define a slot extending transversely through the core, and means are arranged with respect to the slot for reducing the magnetically effective width of the slot and define a remaining gap for reducing core remanence. In this way it is possible to substantially reduce the thickness of the cover plates for the magnet cores, and under certain circumstances, to dispense with the cover plates entirely. The width of the slot can be reduced by inserting ferromagnetic parts, preferably parts having a magnetic conductivity different than the magnetic conductivity of the stacked magnet sheets. Or, a mixture of synthetic material and iron powder may be inserted in the slot, this mixture also serving to subsequently strengthen the metal sheets at their respective openings.

Subsidiary to the first aforementioned feature of the invention, it is an especially advantageous feature of the invention to overlap the slitlike openings with respect to each other. The openings are positioned in the sheets from the centerline of the sheet so that by an alternating stacking of the sheets, the respective openings overlap and jointly define a gap having the desired width for reducing core remanence.

A measuring rule has shown itself to be especially advantageous with which the material of the core at a cross section thereof taken lengthwise through the slot has l to percent of the residual magnetism occurring at a full section of the core. With this dimensioning, the release pressure force that the release spring of a contactor is required to produce is stronger than the remanence force.

The invention will now be described with reference to the drawing wherein:

FIG. 1 illustrates a U-shaped laminated magnet wherein the stacked metal sheets of the magnet core have respective slitlike openings as required by the invention;

FIG. 2, illustrates a laminated magnet core wherein the stacked metal sheets have respective openings which partly overlap each other and jointly define a gap for reducing core remanence;

FIG. 3 illustrates a portion of the bight of the U-shaped laminated magnet core of FIG. 1 together with a ferromagnetic part dimensioned so as to be insertable in the slot defined by the overlapping openings of the respective metal sheets, the ferromagnetic part acting to reduce the magnetically effective width of the slot and define the remaining gap for reducing the core remanence; and

FIG. 4 illustrates the arrangement of FIG. 3 wherein the ferromagnetic part is a mixture of synthetic material and iron powder disposed in the slot.

Referring to FIG. 1, the metal sheets of the magnet core I are designated by reference numeral 2. The metal sheets 2 are provided with openings 3 that are symmetrical with the centerline of the individual metal sheets 2. These openings may be produced for example by stamping. The remaining portion or carrying portion of the respective metal plates is designated by reference numeral 4. The openings 3 overlap and are in mutual alignment so as to define a slot extending transversely through the core 1, the slot being fillable by a ferromagnetic part, in such a manner that a specific airgap remains.

Such a ferromagnetic part is illustrated in FIG. 3. It is also possible to fill the slot with a mixture of synthetic material, preferably epoxy resin, and iron powder, whereby the stability of the total magnet core 1 is increased. FIG. 4 illustrates a magnet core wherein a slot has been filled with such a mixture 7.

In the embodiment of the invention according to FIG. 2, the openings 3 in the respective metal sheets 2 are positioned displaced with respect to the centerline of these sheets. In an alternating layering of the sheets, the openings only partly overlap each other, so that only a relatively smaller airgap 5 is defined for reducing the core remanence. The arrangement according to FIG. 2 affords the advantage that the airgap can be produced without the need of additional parts, namely, simply by stacking the metal sheets in an alternating manner so that the respective openings partially overlap.

The laminated magnet core according to the invention can be produced using conventional stamping tools, so that the cover plates of the known arrangements require a substantially reduced thickness, if they may not indeed be dispensed with entirely. The rigidity of the magnet core according to FIG. 2 has shown itself to be very satisfactory.

Upon a study of this disclosure it will be apparent to those skilled in the art that our invention permits of various other modifications and uses and consequently may be given embodiments other than particularly illustrated and described herein, without departing from the essential features of our invention and within the scope of the claims annexed hereto.

We claim:

l. A laminated magnet core for contactors and the like having a working airgap, said magnet core comprising stacked metal sheets having respective slitlike openings extending across a portion of the width of said sheets, said openings being at least partly overlapping and jointly defining a gap for reducing the core remanence.

2. In a magnet core according to claim 1, said core having a centerline, the respective longitudinal axes of said openings being displaced with respect to said centerline, said sheets being stacked in an alternating manner so that said openings partially overlap so as to jointly define an airgap for reducing the core remanence.

3. In a magnet core according to claim I, said core being U- shaped, said gap being in the bight portion of the U-shape.

4. In a magnet core according to claim I, the material of said core at section thereof taken lengthwise through said slot having l0 to 20 percent of the residual magnetism occurring at a full section of said core.

5. In a magnet core according to claim 1, said openings being in mutual alignment and defining a slot extending transversely through said core and means arranged with respect to said slot for reducing the magnetically effective width of said slot and defining a remaining gap for reducing the core remanence.

6. In a magnet core according to claim 5, said means being a plurality of ferromagnetic parts inserted in said slot.

7'. in a magnet core according to claim 5, said means being a mixture of synthetic material and iron powder disposed in said slot.

k k k i it 

1. A laminated magnet core for contactors and the like having a working airgap, said magnet core comprising stacked metal sheets having respective slitlike openings extending across a portion of the width of said sheets, said openings being at least partly overlapping and jointly defining a gap for reducing the core remanence.
 2. In a magnet core according to claim 1, said core having a centerline, the respective longitudinal axes of said openings being displaced with respect to said centerline, said sheets being stacked in an alternating manner so that said openings partially overlap so as to jointly define an airgap for reducing the core remanence.
 3. In a magnet core according to claim 1, said core being U-shaped, said gap being in the bight portion of the U-shape.
 4. In a magnet core according to claim 1, the material of said core at section thereof taken lengthwise through said slot having 10 to 20 percent of the residual magnetism occurring at a full section of said core.
 5. In a magnet core according to claim 1, said openings being in mutual alignment and defining a slot extending transversely through said core and means arranged with respect to said slot for reducing the magnetically effective width of said slot and defining a remaining gap for reducing the core remanence.
 6. In a magnet core according to claim 5, said means being a plurality of ferromagnetic parts inserted in said slot.
 7. In a magnet core according to claim 5, said means being a mixture of synthetic material and iron powder disposed in said slot. 